Radio communication apparatus and radio communication method

ABSTRACT

A radio communication apparatus performing radio communication based on either role, a master or a slave, includes a role change receiver receiving a role change request from a slave to a master when the radio communication apparatus has a role of slave and has established connection to another radio communication apparatus operating as a master, and a receiver awaiting identification information transmitted by the other radio communication apparatus by receiving multiple channels including a given channel in a given pattern when the role change receiver receives the change request. The receiver receives the multiple channels in the given pattern such that the time or number of times of awaiting the identification information on the given channel is longer or higher than a given comparison criterion for when the role change receiver does not receive the change request

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Divisional of U.S. app. Ser. No. 15/321,696, filed Dec. 22,2016, which is a U.S. National Phase application of PCT/JP2015/066304,filed Jun. 5, 2015, which is based upon and claims the benefit ofpriority from prior Japanese Patent Application No. 2014-134138, filedJun. 30, 2014, the entire contents of all of which are incorporatedherein by reference.

TECHNICAL FIELD

The present disclosure relates to a radio communication apparatus andradio communication method.

BACKGROUND ART

There are techniques for multiple radio communication apparatuseswirelessly communicating with each other, with which each having apredetermined role set, the communication apparatuses perform radiocommunication based on their roles. For example, Unexamined JapanesePatent Application Kokai Publication No. 2013-229805 discloses atechnique for wireless gigabit (WiGig) communication, with which a radiocommunication apparatus, for which one of two roles, “station (STA)” and“personal basic service set central point (PCP),” is set, determineswhether it is necessary to change its own role in making an attempt toconnect to another radio communication apparatus, and when the change isnecessary, switches the role of the other radio communication apparatusand its own role and makes connection to the other radio communicationapparatus.

CITATION LIST Patent Literature

Patent Literature 1: Unexamined Japanese Patent Application KokaiPublication No. 2013-229805

SUMMARY OF INVENTION Technical Problem

Moreover, in a radio communication system performing radio communicationbased on the Bluetooth (registered trademark) low energy, which is ashort range radio communication standard, radio communicationapparatuses operate based on one of two roles, a master taking thecontrol of radio communication and a slave wirelessly communicatingunder the control of the master, while the connection is established.Moreover, a radio communication apparatus having many functions such asa smart-phone can operate both as a master and as a slave. Therefore,for example, a radio communication apparatus operating as a master maybe desired during communication to change to a slave consuming lesspower for reducing the battery drain in some situations. However, forchanging the role, the connection to the other communication apparatusshould once be terminated. Once the connection is terminated, it is notguaranteed that connection is made to the same radio communicationapparatus again. Therefore, smooth reconnection after role switching isdemanded

The present disclosure is made with the view of the above problem and anobjective of the disclosure is to provide a radio communicationapparatus and radio communication method allowing for smooth roleswitching.

Solution to Problem

In order to achieve the above objective, the radio communicationapparatus according to a first exemplary aspect of the presentdisclosure is a radio communication apparatus performing radiocommunication based on either role, a master or a slave, comprising:

a role change receiver receiving a role change request from a master toa slave when the radio communication apparatus has a role of master andhas established connection to another radio communication apparatusoperating as a slave; and

an identification information transmitter transmitting identificationinformation to the other radio communication apparatus on a givenchannel at shorter time intervals when the role change receiver receivesthe change request than a given comparison criterion for when the rolechange receiver does not receive the change request.

In order to achieve the above objective, the radio communicationapparatus according to a second exemplary aspect of the presentdisclosure is a radio communication apparatus performing radiocommunication based on either role, a master or a slave, comprising:

a role change receiver receiving a role change request from a slave to amaster when the radio communication apparatus has a role of slave andhas established connection to another radio communication apparatusoperating as a master; and

a receiver awaiting identification information transmitted by the otherradio communication apparatus by receiving multiple channels including agiven channel in a given pattern when the role change receiver receivesthe change request,

wherein the receiver receives the multiple channels in the given patternsuch that the time or number of times of awaiting the identificationinformation on the given channel is longer or higher than a givencomparison criterion for when the role change receiver does not receivethe change request.

In order to achieve the above objective, the radio communicationapparatus according to a third exemplary aspect of the presentdisclosure is a radio communication apparatus performing radiocommunication based on either role, a master or a slave, comprising:

a role change receiver receiving a role change request from a master toa slave when the radio communication apparatus has a role of master andhas established connection to another radio communication apparatusoperating as a slave;

a disconnector disconnecting from the other radio communicationapparatus when the role change receiver receives the change request; and

an identification information transmitter transmitting identificationinformation to the other radio communication apparatus when it isdetermined that the disconnector disconnects from the other radiocommunication apparatus.

In order to achieve the above objective, the radio communication methodaccording to a fourth exemplary aspect of the present disclosure is aradio communication method executed by a radio communication apparatusperforming radio communication based on either role, a master or aslave, including:

a role change reception step of receiving a role change request from amaster to a slave when the radio communication apparatus has a role ofmaster and has established connection to another radio communicationapparatus operating as a slave; and

an identification information transmission step of transmittingidentification information to the other radio communication apparatus ona given channel at shorter time intervals when the change request isreceived in the role change reception step than a given comparisoncriterion for when the change request is not received in the role changereception step.

In order to achieve the above objective, the radio communication methodaccording to a fifth exemplary aspect of the present disclosure is aradio communication method executed by a radio communication apparatusperforming radio communication based on either role, a master or aslave, including:

a role change reception step of receiving a role change request from aslave to a master when the radio communication apparatus has a role ofslave and has established connection to another radio communicationapparatus operating as a master; and

a reception step of awaiting identification information transmitted bythe other radio communication apparatus by receiving multiple channelsincluding a given channel in a given pattern when the change request isreceived in the role change reception step,

wherein in the reception step, the multiple channels are received in thegiven pattern such that the time or number of times of awaiting theidentification information on the given channel is longer or higher thana given comparison criterion for when the change request is not receivedin the role change reception step.

Advantageous Effects of Invention

The present disclosure can provide a radio communication apparatus andradio communication method allowing for smooth role switching.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing an exemplary configuration of the radiocommunication system according to Embodiment 1;

FIG. 2 is a schematic block diagram showing an exemplary configurationof the radio communication apparatus according to Embodiment 1;

FIG. 3 is a schematic block diagram showing an exemplary functionalconfiguration of the controller of the radio communication apparatusaccording to Embodiment 1;

FIG. 4A is a chart showing chronological transitions of the scanning andadvertising according to Embodiment 1;

FIG. 4B is a chart showing chronological transitions of the scanning andadvertising in the prior art;

FIG. 5 is a sequence chart showing an exemplary operation of the radiocommunication system in Embodiment 1;

FIG. 6 is a flowchart showing an example of the role switching procedure(a) executed by the radio communication apparatus according toEmbodiment 1;

FIG. 7 is a flowchart showing an example of the role switching procedure(b) executed by the radio communication apparatus according toEmbodiment 1;

FIG. 8 is a chart showing chronological transitions of the scanning andadvertising according to Embodiment 2;

FIG. 9 is a chart showing chronological transitions of the scanning andadvertising according to Embodiment 3; and

FIG. 10 is a chart showing chronological transitions of the scanning andadvertising according to Embodiment 4.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure will be described hereafter withreference to the drawings.

Embodiment 1

FIG. 1 is a diagram presenting an exemplary configuration of a radiocommunication system 1 according to Embodiment 1 of the presentdisclosure.

In the exemplary configuration shown in FIG. 1, the radio communicationsystem 1 comprises two radio communication apparatuses 100 (100 a and100 b). The radio communication apparatuses 100 wirelessly communicatewith each other based on the Bluetooth (registered trademark) low energy(BLE, hereafter). The BLE is a standard (mode) designed with intent topursue low power consumption in a short range radio communicationstandard called the Bluetooth (registered trademark). A radiocommunication apparatus 100 operates based on either role, a master or aslave, during radio communication with another radio communicationapparatus 100. For example, a radio communication apparatus 100operating as a master uses services (for example, measurement data)provided from a radio communication apparatus 100 operating as a slave.Moreover, for example, a radio communication apparatus 100 operating asa slave provides services (for example, measurement data) to a radiocommunication apparatus 100 operating as a master.

The radio communication apparatuses 100 are, for example, devices suchas cell-phones, smart-phones, tablet-type personal computers, andnote-type personal computers and terminals capable of radiocommunication based on the BLE as well. When functioning as a master, aradio communication apparatus 100 receives various data from a radiocommunication apparatus 100 functioning as a slave and displays variouskinds of information on a display 107 described later and produces soundsuch as an alarm from a speaker 106 described later based on thereceived data. Moreover, when functioning as a slave, a radiocommunication apparatus 100 notifies a radio communication apparatus 100functioning as a master of a summary of services its own apparatusretains and transmits an advertisement for awaiting a connection requestfrom the master.

The hardware configuration of the radio communication system 1 accordingto Embodiment 1 will be described hereafter.

FIG. 2 is a block diagram schematically showing an exemplary hardwareconfiguration of the radio communication apparatuses 100 according toEmbodiment 1. As shown in FIG. 2, a radio communication apparatus 100comprises a controller 101, a read only memory (ROM) 102, a randomaccess memory (RAM) 103, a radio communication processor 104, an antenna105, a speaker 106, a display 107, and an operator 108.

The controller 101 comprises, for example, a central processing unit(CPU). The controller 101 executes software procedures according toprograms stored in the ROM 102 (for example, programs for realizing therole switching procedures (a) and (b) shown in FIGS. 6 and 7 describedlater) to control various functions provided to the radio communicationapparatus 100.

The ROM 102 comprises a nonvolatile memory such as a flash memory andstores programs and data for the controller 101 to control variousfunctions as described above.

The RAM 103 comprises a volatile memory and is used as the work area forthe controller 101 to temporarily store data for executing variousprocedures.

The radio communication processor 104 comprises, for example, a radiofrequency (RF) circuit, base band (BB) circuit, memory circuit, and thelike. The radio communication processor 104 transmits and receives radiosignals based on the BLE via the antenna 105. Moreover, the memorycircuit of the radio communication processor 104 is used as a region tostore and update a white list (details are described later).

The speaker 106 outputs sound such as an alarm based on sound data fromthe controller 101. The display 107 comprises, for example, a liquidcrystal display (LCD), electroluminescence (EL) display, a driver, andthe like. The display 107 displays images according to image signalsoutput from the controller 101.

The operator 108 is an interface used for receiving user operationcontents and comprises, for example, an input apparatus such as a touchpanel, buttons, and a keyboard. The operator 108 outputs receivedoperation contents to the controller 101.

The functions of the controller 101 of the radio communicationapparatuses 100 will be described hereafter. FIG. 3 is a schematic blockdiagram showing an exemplary functional configuration of the controller101 of the radio communication apparatuses 100. As shown in FIG. 3, thecontroller 101 functions as a role change receiver 111, a role changeconfirmer 112, a disconnector 113, an advertisement transmitter 114, ascanner 115, a connection establisher 116, and a data communicator 117.The role change receiver 111, role change confirmer 112, disconnector113, advertisement transmitter 114, scanner 115, connection establisher116, and data communicator 117 may be a single CPU or may each be a CPUperforming individual operation.

The role change receiver 111 receives a change request for changing thecurrent role to the other role between two roles, a master and a slave,while connection to another radio communication apparatus 100 isestablished.

For example, the role change receiver 111 receives a change requestbased on convenience of its own communication apparatus 100.Specifically, the role change receiver 111 determines that a role changerequest from a master to a slave is received when, for example, its ownradio communication apparatus 100 currently operates as a master and isvery low in the remaining battery level. As a result of such a rolechange, the radio communication apparatus 100 can operate as a slavethat consumes less power than a master.

Moreover, the role change receiver 111 may receive a change request fromanother radio communication apparatus 100. The role change receiver 111determines that a change request is received when, for example, a changerequest for changing the current role to the other role is received fromanother radio communication apparatus 100 to which connection isestablished.

When the role change receiver 111 receives a change request based onconvenience of its own radio communication apparatus 100, the rolechange confirmer 112 inquires of another radio communication apparatus100 to which connection is established about the possibility of rolechange from the current role to the other role. Then, if the other radiocommunication apparatus 100 can change the role, the role changeconfirmer 112 transmits a request for switching the role (a roleswitching request).

Moreover, when the role change receiver 111 receives a change requestfrom another radio communication apparatus 100 to which connection isestablished, the role change confirmer 112 responds to the other radiocommunication apparatus 100 as to whether its own radio communicationapparatus 100 can change the role. Then, when a role switching requestis received from the other radio communication apparatus 100, the rolechange confirmer 112 transmits a response to the role switching requestto the other radio communication apparatus 100. Moreover, the rolechange confirmer 112 includes information regarding an advertisingchannel after disconnection (details will be described later) as aparameter in the response to the role switching request along with thepossibility of role change

Here, for example, it is possible to define a new bit presenting thepossibility of role change among bits reserved for future use (RFU)prepared in the feature set of a link layer. Then, the radiocommunication apparatus 100 having received an inquiry about thepossibility of role change has only to check the bit presenting thepossibility of role change defined in the RFU and include information ofthe bit in the response to the inquiry.

Furthermore, the role change confirmer 112 registers a radiocommunication apparatus 100 to which connection is currently establishedas the communication partner on the white list set in the link layer.Here, reading the white list is not defined by the current host controlinterface (HCI) commands and therefore, has to be newly defined. Here,instead of defining a new command, information of addition of a deviceto the current white list may also be retained on the host side. In thisway, the current while list is backed up on the host side and both radiocommunication apparatuses 100 switching their roles use the white liston which only the radio communication apparatus 100 of the roleswitching partner is set to advertise or scan, whereby it is possible toreconnect certainly to the role switching partner. Here, after thereconnection is completed or even when the reconnection is unsuccessful,information of the white list changed for the reconnection can berestored based on the information backed up on the host side.

The disconnector 113 terminates the connection when the role changeconfirmer 112 determines to switch the role with another radiocommunication apparatus 100 to which connection is established.

The advertisement transmitter 114 transmits an advertisement on oneadvertising channel set by the role change confirmer 112 when the rolechange confirmer 112 determines to switch the role from a master to aslave.

Here, advertising in radio communication based on the BLE is described.In the BLE-based radio communication, one radio communication apparatus100 (advertiser) transmits an advertisement and another radiocommunication apparatus 100 (scanner) scans to receive the advertisementbefore connection is established. An advertisement or advertising meansa packet or transmitting/receiving a packet including identificationinformation for notifying another radio communication apparatus of itsown presence in search for another radio communication apparatus or inan attempt to make connection to another radio communication apparatus.

In the BLE, a frequency band of 2400 MHz to 2483.5 MHz is divided into40 channels of 2 MHz each in width. Among the 40 channels, threeadvertising channels having an intermediate frequency (RF centerfrequency) of 2402, 2426, or 2480 MHz (of which the advertising channelindices are 37, 38, and 39) are used for advertising. The other 37 datacommunication channels (of which the data channel indices are 0 to 36)are used for data communication after connection between a master andslave is established.

Here, in the prior art BLE-based radio communication, slaves advertisealways using the above three channels. Conversely, in the radiocommunication system 1 according to Embodiment 1, when attempting tomake reconnection to a radio communication apparatus 100 with which therole change from a slave to a master is determined, the advertisementtransmitter 114 advertises using a given one advertising channel set inthe response to the role switching request from the role changeconfirmer 112. Here, which channel is used as an advertising channelamong the channels 37, 38, and 39 is, for example, preset by the user.

Furthermore, in the radio communication system 1 according to Embodiment1, the advertisement transmitter 114 transmits an advertisement atintervals I1 (for example, 10 milliseconds) shorter than normaladvertising intervals I0 (for example, 1 second) during a given timeperiod T1 since the start of transmitting an advertisement as shown inFIG. 4A. Then, after the given time period T1 has elapsed, theadvertisement transmitter 114 transmits an advertisement at the normaladvertising intervals I0. Here, the normal advertising intervals areintervals at which the radio communication apparatus 100 transmits anadvertisement when no role switching is conducted.

The scanner 115 scans for an advertisement on three advertising channelswhen the role change confirmer 122 determines to change the role from aslave to a master.

Parameters defining the scanning of the scanner 115 include a scanwindow and a scan interval. The scan window is a time during whichscanning is actually performed. On the other hand, the scan intervalindicates the intervals between adjoining scan windows. When the scanwindow and scan interval are equal, successive scanning is performed.The BLE specification recommends scanning only one channel in each scanwindow and changing a scanning channel every scan window, and statesthat all three channels should definitely be scanned. In Embodiment 1,the scanner 115 repeatedly scans the three advertising channels 37 to 39in the order of 37, 38, 39, 37, 38, 39, . . . at an equal frequency asshown in FIG. 4A.

The time until an advertisement transmitted by the advertisementtransmitter 114 of a radio communication apparatus 100 is received bythe scanner 115 of another radio communication apparatus 100 will bedescribed hereafter. FIG. 4A is a chart showing chronologicaltransitions of the scanning and advertising according to Embodiment 1.On the other hand, FIG. 4B is a chart showing chronological transitionsof the scanning and advertising in the prior art. Here, in both FIGS. 4Aand 4B, it is assumed that an advertisement is transmitted on thechannel 38. As shown in FIG. 4B, in the prior art advertising, anadvertisement is transmitted at the normal advertising intervals I0 andthe advertisement transmitted first since the start of scanning thechannel 38 is scanned at a time tb. On the other hand, in FIG. 4A, anadvertisement is transmitted first at the advertising intervals I1shorter than the I0 and the advertisement transmitted first since thestart of scanning the channel 38 is scanned at a time to earlier thanthe time tb. In other words, an advertisement is transmitted morefrequently for a given time period T1 since the start of advertising,whereby it is possible to quickly scan an advertisement whilesuppressing power consumption as much as possible. As described above,the scanner 115 functions as a receiver receiving an advertisementtransmitted from another radio communication apparatus 100.

When the role change confirmer 112 determines to change the role from amaster to a slave and a connection request is received from anotherradio communication apparatus 100 with respect to an advertisementtransmitted by the advertisement transmitter 114, the connectionestablisher 116 establishes connection in response to the connectionrequest if the other radio communication apparatus 100 is registered onthe white list.

Moreover, when the role change confirmer 112 determines to change therole from a slave to a master and the scanner 115 receives anadvertisement from another radio communication apparatus 100 registeredon the white list, the connection establisher 116 transmits a connectionrequest to the other radio communication apparatus 100 and establishesconnection.

After the connection establisher 116 establishes connection to the otherradio communication apparatus 100, the data communicator 117 performsdata communication with the other radio communication apparatus 100 onthe 37 data communication channels based on the role determined by therole change confirmer 112.

An exemplary operation of the radio communication system 1 according toEmbodiment 1 will be described hereafter with reference to the sequencechart in FIG. 5. In the example shown in FIG. 5, operations of the hostand link layer of the radio communication apparatuses 100 a and 100 bare described using a case in which the first radio communicationapparatus 100 a operating as a slave and the second radio communicationapparatus 100 b operating as a master switch their roles while theirconnection is established.

Triggered by a low battery level of its own apparatus, the second radiocommunication apparatus 100 b transmits to the first radio communicationapparatus 100 a an inquiry about functions supported by the link layerof the first radio communication apparatus 100 a (LL_FEATURE_REQ) inorder to check whether the role switching with the first radiocommunication apparatus 100 a is possible (Step S10).

Then, the first radio communication apparatus 100 a having received theLL_FEATURE_REQ determines whether the role switching is supported withreference to FeatureSet presenting the link layer-supported functions.If the role switching is supported, the first radio communicationapparatus 100 a transmits a response indicating that the role switchingis supported (LL_FEATURE_RSP) to the second radio communicationapparatus 100 b (Step S11).

Then, as the second radio communication apparatus 100 b receives theresponse indicating that the role switching is supported from the firstradio communication apparatus 100 a, the host of the second radiocommunication apparatus 100 b outputs a role switching order to the linklayer (Step S12). Then, the link layer of the second radio communicationapparatus 100 b transmits a role switching request (ROLE_SWITCH_REQ) tothe first radio communication apparatus 100 a (Step S13) and notifiesthe host of the completion (Step S14).

Receiving the role switching request, the link layer of the first radiocommunication apparatus 100 a notifies the host of reception of a roleswitching request (Step S15). Then, the host orders the link layer torespond to the second radio communication apparatus 100 b that the roleswitching is possible when the first radio communication apparatus 100 ahas a sufficient remaining battery level and the role change to a masteris possible (Step S16). Then, the link layer transmits a responseindicating that the role switching is possible (ROLE_SWITCH_RSP) to thesecond radio communication apparatus 100 b along with informationpresenting an advertising channel used for advertising upon reconnection(Step S17) and notifies the host of the completion (Step S18).

As the link layer of the second radio communication apparatus 100 breceives the response indicating that the role switching is possiblefrom the first radio communication apparatus 100 a, the host of thesecond radio communication apparatus 100 b orders the link layer to readthe white list (Step S19). Then, the link layer reads data presentingthe radio communication apparatuses 100 registered on the white list andnotifies the host of the completion (Step S20).

Then, the host of the second radio communication apparatus 100 b ordersthe link layer to clear the read data on the white list (Step S21).Then, the link layer clears the data and notifies the host of thecompletion (Step S22).

Then, the host of the second radio communication apparatus 100 b ordersthe link layer to add data presenting the first radio communicationapparatus 100 a to the white list (Step S23). Then, the link layer addsdata presenting the first radio communication apparatus 100 a to thewhite list and notifies the host of the completion (Step S24).

Moreover, the first radio communication apparatus 100 a performs thesame processing as in the Steps S19 to S24 in Steps S25 to S30.

Then, the host of the second radio communication apparatus 100 b ordersthe link layer to disconnect from the first radio communicationapparatus 100 a (Step S31). Then, the link layer transmits adisconnection request (TERMINATE_IND) to the first radio communicationapparatus 100 a (Step S32) and notifies the host of the completion (StepS33).

Moreover, receiving the disconnection request, the link layer of thefirst radio communication apparatus 100 a notifies the host of thecompletion of disconnection from the second radio communicationapparatus 100 b (Step S34).

Then, the host of the second radio communication apparatus 100 b ordersthe link layer to set advertising data (Step S35). After completing thesetting of advertising data, the link layer notifies the host of thecompletion (Step S36).

Then, the host of the second radio communication apparatus 100 b ordersthe link layer to set advertising parameters (Step S37). Aftercompleting the setting of advertising parameters, the link layernotifies the host of the completion (Step S38).

Then, the host of the second radio communication apparatus 100 b ordersthe link layer to start advertising (Step S39). The link layer notifiesthe host of the completion (Step S40) and transmits an advertisement atadvertising intervals shorter than the normal advertising intervals(Step S41).

Moreover, the host of the first radio communication apparatus 100 aorders the link layer to set scanning parameters (Step S42). Aftercompleting the setting of scanning parameters, the link layer notifiesthe host of the completion (Step S43).

Then, the host of the first radio communication apparatus 100 a ordersthe link layer to start scanning (Step S44). The link layer notifies thehost of the completion (Step S45) and scans three advertising channelsin sequence at given time intervals.

As it is determined that an advertisement is received from the secondradio communication apparatus 100 b registered on the white list, thelink layer of the first radio communication apparatus 100 a notifies thehost of the reception of an advertisement (Step S46). The host ordersthe link layer to make connection to the second radio communicationapparatus 100 b (Step S47) and the link layer returns a command statusto the host (Step S48).

Then, receiving an advertisement from the second radio communicationapparatus 100 b, the link layer of the first radio communicationapparatus 100 a transmits a connection request (CONNECT_REQ) to thesecond radio communication apparatus 100 b (Step S49) and completesestablishment of connection to the second radio communication apparatus100 b (Step S50). From then on, the first radio communication apparatus100 a performs data communication as a master with the second radiocommunication apparatus 100 b.

Moreover, receiving the connection request from the first radiocommunication apparatus 100 a, the link layer of the second radiocommunication apparatus 100 b completes establishment of connection tothe first radio communication apparatus 100 a (Step S51). From then on,the second radio communication apparatus 100 b performs datacommunication as a slave with the first radio communication apparatus100 a.

Operation of the radio communication apparatus 100 according toEmbodiment 1 will be described hereafter with reference to FIGS. 6 and7. FIG. 6 is a flowchart showing an example of the role switchingprocedure (a) executed by the controller 101 of a radio communicationapparatus 100 according to Embodiment 1. In this role switchingprocedure (a), a case is described in which a second radio communicationapparatus 100 b operating as a master changes its role to a slave whileconnection to a first radio communication apparatus 100 a operating as aslave is established. The role switching procedure (a) is executed bythe controller 101 of the second radio communication apparatus 100 b.

The role switching procedure (a) shown in FIG. 6 starts when, forexample, it is determined that the role change receiver 111 receives arole change request as the remaining battery level of its own apparatusbecomes equal to or lower than a given value.

First, the role change confirmer 112 transmits to the first radiocommunication apparatus 100 a an inquiry about functions supported bythe link layer of the first radio communication apparatus 100 a(LL_FEATURE_REQ) (Step S101). Then, the role change confirmer 112determines whether a response to the inquiry (LL_FEATURE_RSP) isreceived from the first radio communication apparatus 100 a (Step S102).The role change confirmer 112 awaits until a response is received (StepS102; No).

If a response to the inquiry (LL_FEATURE_RSP) is received from the firstradio communication apparatus 100 a (Step S102; Yes), the role changeconfirmer 112 determines whether the first radio communication apparatus100 a supports the role switching based on the received response (StepS103).

If the first radio communication apparatus 100 a supports the roleswitching (Step S103; Yes), the role change confirmer 112 transmits arole switching request (ROLE_SWITCH_REQ) to the first radiocommunication apparatus 100 a (Step S104). Then, the role changeconfirmer 112 determines whether a response to the role switchingrequest (ROLE_SWITCH_RES) is received from the first radio communicationapparatus 100 a (Step S105). The role change confirmer 112 awaits untila response is received (Step S105; No).

If a response to the role switching request (ROLE_SWITCH_RES) isreceived from the first radio communication apparatus 100 a (Step S105;Yes), the role change confirmer 112 determines whether the first radiocommunication apparatus 100 a can switch the role based on the receivedresponse (Step S106).

If the first radio communication apparatus 100 a can switch the role(Step S106; Yes), the role change confirmer 112 executes an advertisingparameter setting procedure to set advertising parameters (Step S107).Among the advertising parameters to set here, the advertising intervalsthat are intervals between advertising operations are set to a valueshorter than the normal advertising intervals. Moreover, the response tothe role switching request (ROLE_SWICTH_RSP) includes data presenting anadvertising channel Moreover, the role change confirmer 112 registersthe address of the first radio communication apparatus 100 a on thewhite list.

Then, the disconnector 113 transmits a disconnection request(TERMINATE_IND) to the first radio communication apparatus 100 a (StepS108). Then, the disconnector 113 disconnects from the first radiocommunication apparatus 100 a.

Then, the advertisement transmitter 114 starts advertising using theparameters set in the Step S107 and the advertising channel notified inthe response to the role switching request (ROLE_SWICTH_RSP).

The connection establisher 116 determines whether a connection request(CONNECT_REQ) is received from the first radio communication apparatus100 a registered on the white list (Step S110).

If the connection establisher 116 determines that a connection requestis received from the first radio communication apparatus 100 a (StepS110; Yes), the advertisement transmitter 114 stops advertising (StepS111).

The connection establisher 116 executes a procedure to establishconnection to the first radio communication apparatus 100 a usingconnection parameters included in the received connection request (StepS112). Then, the connection establisher 116 ends the role switchingprocedure (a). After this procedure ends, the second radio communicationapparatus 100 b operates as a slave and performs data communication withthe first radio communication apparatus 100 a operating as a master.

On the other hand, if the connection establisher 116 determines that noconnection request is received from the first radio communicationapparatus 100 a (Step 5110; No), the advertisement transmitter 114determines whether a given time period T1 has elapsed since the start ofadvertising (Step S113). If the given time period T1 has not elapsed(Step S113; No), the advertisement transmitter 114 returns theprocessing to the Step S110.

If the given time period T1 has elapsed (Step S113; Yes), theadvertisement transmitter 114 changes the advertising intervals to thenormal value and continues to advertise (Step S114).

Then, the connection establisher 116 determines whether a connectionrequest (CONNECT_REQ) is received from the first radio communicationapparatus 100 a registered on the white list (Step S115).

If a connection request is received from the first radio communicationapparatus 100 a (Step S115; Yes), the connection establisher 116advances the processing to Step S111. On the other hand, if noconnection request is received from the first radio communicationapparatus 100 a (Step S115; No), the advertisement transmitter 114determines whether a given time period T2 (T2>T1) has elapsed since thestart of advertising (Step S116). If the given time period T2 has notelapsed (Step S116; No), the advertisement transmitter 114 returns theprocessing to the Step S115.

If the given time period T2 has elapsed (Step S116; Yes), the connectionestablisher 116 determines that reconnection to the first radiocommunication apparatus 100 a is unsuccessful and ends the roleswitching procedure (a).

On the other hand, if the role change confirmer 112 determines that thefirst radio communication apparatus 100 a does not support the roleswitching (Step S103; No), or determines that the first radiocommunication apparatus 100 a cannot switch the role (Step S106; No),the disconnector 113 disconnects from the first radio communicationapparatus 100 a (Step S117) and ends the role switching procedure (a).

The role switching procedure (b) executed by the controller 101 of aradio communication apparatus 100 according to Embodiment 1 and shown inFIG. 7 by way of example will be described hereafter. In this roleswitching procedure (b), a case is described in which a first radiocommunication apparatus 100 a operating as a slave changes its role to amaster while connection to a second radio communication apparatus 100 boperating as a master is established. The role switching procedure (b)is executed by the controller 101 of the first radio communicationapparatus 100 a.

The role switching procedure (b) shown in FIG. 7 starts when, forexample, the role change receiver 111 receives a role switching request(ROLE_SWITVH_REQ) from the second radio communication apparatus 100 b.

First, the role change confirmer 112 determines whether its ownapparatus can switch the role (Step S201). The role change confirmer 112determines that its own apparatus can switch the role when, for example,the remaining battery level of its own apparatus is equal to or higherthan a given value.

Then, if its own apparatus can switch the role (Step S201; Yes), therole change confirmer 112 transmits a response indicating that the roleswitching is possible (ROLE_SWITCH_RSP (OK)) to the second radiocommunication apparatus 100 b (Step S202). Moreover, the role changeconfirmer 112 includes data presenting an advertising channel in theresponse.

Then, the role change confirmer 112 executes a scanning parametersetting procedure to set scanning parameters (Step S203). Moreover, therole change confirmer 112 registers the address of the second radiocommunication apparatus 100 b on the white list.

Then, the disconnector 113 determines whether a disconnection request(TERMINATE_IND) is received from the second radio communicationapparatus 100 b (Step S204). The disconnector 113 awaits until adisconnection request is received (Step S204; No).

If a disconnection request is received from the second radiocommunication apparatus 100 b (Step S204; Yes), the disconnector 113disconnects from the second radio communication apparatus 100 b. Then,the scanner 115 starts scanning using the parameters set in the StepS203 (Step S205).

The connection establisher 116 determines whether an advertisement isreceived from the second radio communication apparatus 100 b registeredon the white list (Step S206).

If the connection establisher 116 determines that an advertisement isreceived from the second radio communication apparatus 100 b (Step S206;Yes), the scanner 115 stops scanning (Step S207).

Then, the connection establisher 116 transmits a connection request(CONNECT_REQ) to the second radio communication apparatus 100 b andestablishes connection to the second radio communication apparatus 100 b(Step S208). Then, the role switching procedure (b) ends. After thisprocedure ends, the first radio communication apparatus 100 a operatesas a master and performs data communication with the second radiocommunication apparatus 100 b operating as a slave.

On the other hand, if no advertisement is received from the second radiocommunication apparatus 100 b (Step S206; No), the scanner 115determines whether a given time period T2 has elapsed since the start ofscanning (Step S209). If the given time period T2 has not elapsed (StepS209; No), the scanner 115 returns the processing to the Step S206.

If the given time period T2 has elapsed (Step S209; Yes), the scanner115 stops scanning (Step S210). Then, the connection establisher 116determines that reconnection to the second radio communication apparatus100 b is unsuccessful and ends the role switching procedure (b).

On the other hand, if the first radio communication apparatus 100 acannot switch the role (Step S201; No), the role change confirmer 112transmits a response indicating that the role switching is impossible(ROLE_SWITCH_RSP (NO)) to the second radio communication apparatus 100 b(Step S211). Then, the role change confirmer 112 ends the role switchingprocedure (b).

As described above, the radio communication apparatus 100 according tothe above Embodiment 1 presets an advertising channel while connectionis established and a radio communication apparatus 100 transmitting anadvertisement for reconnection transmits the advertisement on thatadvertising channel. In doing so, the advertisement is transmitted atshorter intervals than normally, whereby the reconnection can be quick.

Moreover, the connected radio communication apparatuses 100synchronously disconnect from each other and then perform theadvertising or scanning, whereby the reconnection can be smooth.

Moreover, a radio communication apparatus 100 operating as a slave afterrole switching receives only a connection request from the radiocommunication apparatus 100 registered on the white list. Moreover, aradio communication apparatus 100 operating as a master after roleswitching receives only an advertisement from the radio communicationapparatus 100 registered on the white list. Therefore, it is possible toprevent connection to a radio communication apparatus other than therole switching partner after the disconnection.

Embodiment 2

In the above Embodiment 1, a radio communication apparatus 100 operatingas a slave after role switching transmits an advertisement at shorterintervals after the disconnection, whereby smooth reconnection isrealized. However, the method of making smooth reconnection is notrestricted thereto. In Embodiment 2, as a scanning method by a radiocommunication apparatus 100 operating as a master after role switching,a case is described in which the first scan since the start of scanningis performed on an advertising channel preset together with the otherradio communication apparatuses 100 for a longer time than the normalscan window and then the scan is performed on the three advertisingchannels in sequence using the normal scan window.

FIG. 8 shows chronological transitions of the scanning and advertisingaccording to Embodiment 2. In FIG. 8, it is assumed that anadvertisement is transmitted on the channel 38 at the normal advertisingintervals I0. As shown in FIG. 8, in the first scan since the start ofscanning, the scanner 115 of the radio communication apparatus 100 scanson the channel 38 that is an advertising channel preset together withanother radio communication apparatus 100 of the role switching partner.A scan window S1 at this point (for example, 10.24 seconds) is longerthan a normal scan window S0 (for example, one second). Here, the normalscan window is a scan window for when no role switching is performed.After finishing scanning on the channel 38, the scanner 115 scans thethree advertising channels in sequence using the normal scan window S0.As just stated, the first scan after the disconnection is a scan on apreset advertising channel for a longer time than the normal scanwindow, whereby quick scan for an advertisement is made possible.

Embodiment 3

As Embodiment 3, another scanning method by a radio communicationapparatus 100 operating as a master after role switching will bedescribed hereafter.

FIG. 9 shows chronological transitions of the scanning and advertisingaccording to Embodiment 3. In FIG. 9, it is assumed that anadvertisement is transmitted on the channel 38 at the normal advertisingintervals I0. As shown in FIG. 9, after starting to scan, the scanner115 of the radio communication apparatus 100 scans the three advertisingchannels in sequence using a scan window S2 (for example, 25milliseconds) shorter than the normal scan window S0. As just stated,using a shorter scan window, it is possible to quickly scan for anadvertisement even if the channel on which an advertisement is sent froma radio communication apparatus 100 of the role switching partner isunknown.

Embodiment 4

As Embodiment 4, another scanning method by a radio communicationapparatus 100 operating as a master after role switching will bedescribed hereafter.

FIG. 10 shows chronological transitions of the scanning and advertisingaccording to Embodiment 4. In FIG. 10, it is assumed that anadvertisement is transmitted on the channel 38 at the normal advertisingintervals I0. As shown in FIG. 10, the scanner 115 of the radiocommunication apparatus 100 scans the three advertising channels in themanner that the advertising channel 38 preset together with anotherradio communication apparatus 100 of the role switching partner isscanned at a higher frequency instead of scanning the three advertisingchannels at an equal frequency. In other words, in the case shown inFIG. 10, the channel 38 is scanned in every other scan window. As juststated, the scanning order is set so that the advertising channel presettogether with another radio communication apparatus 100 of the roleswitching partner is scanned at a higher frequency, whereby it ispossible to quickly scan for an advertisement transmitted from a radiocommunication apparatus 100 of the role switching partner.

Embodiment 5

In conventional BLE-based radio communication, a radio communicationapparatus makes connection using connection parameters included in aconnection request (CONNECT_REQ) packet. However, for reconnection afterrole switching, the radio communication apparatus 100 may take over theconnection parameters used in the connection before the role switching.

Specifically, connection parameters included in a connection requestpacket include AA, CRCInit, WinSize, WinOffset, Interval, Latency,Timeout, ChM, Hop, and SCA.

AA is the access address of a data packet after connection. The value ofAA can be taken over provided that the value is not a duplicate of AA ofany other connection. Moreover, the value can be taken over when asetting of inhibiting any other connection from disconnection toreconnection is enabled.

CRCInit is a value specifying the initial value of a shift registerverifying the checksum of a packet. The value of CRCInit cannot be takenover upon reconnection because it is randomly created by the link layer.

WinSize presents a period during which the first data packet can betransmitted. The value of Win Size can be taken over.

WinOffset presents an offset time from transmission of a connectionrequest to start of the next window size. The value of WinOffset can betaken over when the radio communication apparatus 100 is not busy withother operations after transmitting/receiving a connection request.

Interval presents the intervals of hopping channels. The value ofInterval can be taken over.

Latency presents the number of times of a connection event being ignoredby a radio communication apparatus 100 operating as a slave when thereare no data to transmit to a radio communication apparatus 100 operatingas a master. The value of Latency can be taken over.

Timeout is a time in which connection is determined to be lost. Thevalue of Timeout can be taken over.

ChM is a value specifying which data channel is to use for a connectionevent. The value of ChM can be taken over.

Hop is a value specifying the order of switching data channels. Thevalue of Hop can be taken over.

SCA is a value presenting the accuracy of the sleep clock of a radiocommunication apparatus 100 operating as a master. The value of SCA canbe taken over when a radio communication apparatus 100 operating as amaster and a radio communication apparatus 100 operating as a slave havethe same clock accuracy.

Hence, it may be possible that among the connection parameters used inthe connection before role switching, those that can be taken over areretained after disconnection, and the connection establisher 116 of aradio communication apparatus 100 operating as a master after the roleswitching transmits a connection request including connection parametersthat cannot be taken over and excluding connection parameters that canbe taken over in an attempt to reconnect to a radio communicationapparatus 100 of the role switching partner. As just stated, with asimplified connection request excluding connection parameters that canbe taken over being transmitted, it is possible for a radiocommunication apparatus 100 receiving the connection request to savepower in the reception and in the packet processing.

Embodiments of the present disclosure are described above. The presentdisclosure is not confined to the above embodiments.

For example, in the above embodiments, information presenting anadvertising channel in an attempt to make reconnection afterdisconnection is included in a response to a role switching request byway of example. However, the method of giving notice of an advertisingchannel upon reconnection is not restricted thereto. It is sufficientthat an advertising channel upon reconnection is set by any methodbetween the radio communication apparatuses 100 operating as a slave anda master before they are disconnected. For example, when a radiocommunication apparatus 100 operating as a master transmits a roleswitching request, information presenting an advertising channel uponreconnection may be included in the packet.

Moreover, in the above embodiments, a radio communication apparatus 100operating as a master transmits a role switching request by way ofexample. However, a radio communication apparatus 100 operating as aslave may transmit a role switching request.

Moreover, in the above embodiments, the role switching partner isregistered on the white list by way of example for assuring reconnectionto the role switching partner. However, instead of using the white list,the advertisement transmitter 114 of a radio communication apparatus 100operating as a slave after role switching may use, in advertising, adirect advertisement (ADV_DIRECT_IND) specifying a radio communicationapparatus 100 of the role switching partner as the destination of anadvertisement. The address of the partner has been obtained frominformation in the advertisement upon connection before role switching;therefore, directly advertising to that address can prevent connectionto a radio communication apparatus other than the role switchingpartner.

Moreover, the method of transmitting an advertisement described inEmbodiment 1 and the methods of scanning described in Embodiments 2 to 4may be combined. For example, it may possible that the advertisementtransmitter 114 of a radio communication apparatus 100 operating as aslave after role switching transmits an advertisement on the channel 38at advertising intervals T1 until a given time period T1 elapses sincethe start of advertising and concurrently, the scanner 115 of a radiocommunication apparatus 100 operating as a master after role switchingscans the channel 38 in a scan window S1 in the first scan.

Moreover, in the above embodiments, the radio communication systemperforming radio communication based on the BLE as an exemplary radiocommunication standard is described by way of example. The radiocommunication standard to which the present disclosure is applicable isnot restricted to the BLE and the present disclosure is applicable toother standards of communication between devices operating as a masterand a slave.

Moreover, the radio communication apparatus 100 according to the presentdisclosure can be realized by a conventional computer system, not by adedicated apparatus. For example, a computer may execute programs torealize the functions of the radio communication apparatus 100. Theprograms for realizing the functions of the radio communicationapparatus 100 may be stored on a non-transitory computer-readablerecording medium such as a universal serial bus (USB) memory, securedigital (SD) memory card, compact disc read only memory (CD-ROM),digital versatile disc (DVD), Blu-ray (registered trademark) disc (BD),and hard disk drive (HDD), or downloaded on a computer via a network.

The foregoing describes some example embodiments for explanatorypurposes. Although the foregoing discussion has presented specificembodiments, persons skilled in the art will recognize that changes maybe made in form and detail without departing from the broader spirit andscope of the invention. Accordingly, the specification and drawings areto be regarded in an illustrative rather than a restrictive sense. Thisdetailed description, therefore, is not to be taken in a limiting sense,and the scope of the invention is defined only by the included claims,along with the full range of equivalents to which such claims areentitled.

The present application claims the priority based on Japanese PatentApplication No. 2014-134138, filed on Jun. 30, 2014, and the contents ofthe basic application are all incorporated herein.

1. A radio communication apparatus performing radio communication basedon either role, a master or a slave, comprising: a role change receiverreceiving a role change request from a slave to a master when the radiocommunication apparatus has a role of slave and has establishedconnection to another radio communication apparatus operating as amaster; and a receiver awaiting identification information transmittedby the other radio communication apparatus by receiving multiplechannels including a given channel in a given pattern when the rolechange receiver receives the change request, wherein the receiverreceives the multiple channels in the given pattern such that the timeor number of times of awaiting the identification information on thegiven channel is longer or higher than a given comparison criterion forwhen the role change receiver does not receive the change request. 2.The radio communication apparatus according to claim 1, wherein thereceiver receives the given channel until a first given time elapsessince the start of reception and then receives the multiple channels insequence for a second given time shorter than the first given time. 3.The radio communication apparatus according to claim 1, wherein thereceiver receives the multiple channels in sequence for a time shorterthan the given comparison criterion.
 4. The radio communicationapparatus according to claim 1, wherein the receiver alternatelyreceives the given channel and the channels other than the given channelamong the multiple channels.
 5. The radio communication apparatusaccording to claim 1, further comprising: a role change confirmerinquiring of the other radio communication apparatus about thepossibility of role change from a master to a slave when the role changereceiver receives the change request, wherein the receiver awaitsidentification information transmitted by the other radio communicationapparatus when a response from the other radio communication apparatusto the inquiry from the role change confirmer presents the role changebeing possible.
 6. The radio communication apparatus according to claim1, wherein the role change receiver receives the change request from theother radio communication apparatus.
 7. The radio communicationapparatus according to claim 1, further comprising: a connectionestablisher transmitting a connection request to the other radiocommunication apparatus having transmitted the identificationinformation received by the receiver and establishing connection to theother radio communication apparatus, wherein receiving the changerequest, the role change receiver records in a storage apparatusinformation of the other radio communication apparatus, and whenidentification information is received from another radio communicationapparatus and apparatus information of the other radio communicationapparatus having transmitted the connection request is recorded in thestorage, the connection establisher transmits a connection request tothe other radio communication apparatus having transmitted theidentification information.
 8. The radio communication apparatusaccording to claim 7, wherein the connection establisher takes overconnection parameters used in connection before role change asconnection parameters after role change.
 9. A radio communication methodexecuted by a radio communication apparatus performing radiocommunication based on either role, a master or a slave, including: arole change reception step of receiving a role change request from aslave to a master when the radio communication apparatus has a role ofslave and has established connection to another radio communicationapparatus operating as a master; and a reception step of awaitingidentification information transmitted by the other radio communicationapparatus by receiving multiple channels including a given channel in agiven pattern when the change request is received in the role changereception step, wherein in the reception step, the multiple channels arereceived in the given pattern such that the time or number of times ofawaiting the identification information on the given channel is longeror higher than a given comparison criterion for when the change requestis not received in the role change reception step.